HONG KONG – The claim of a Chinese scientist that he used the genomic fabrication technology CRISPR-Cas9 to change the DNA of human embryos, resulting in the birth a few weeks ago of twin girls, baffled organizers of the International Summit on Human Genomic Practice , leaving them scrambling behind to evaluate the claim two days before the scientist will speak at the meeting.
"I do not know the details" of He Jiankui's claim, said David Baltimore of the California Institute of Technology, chairman of the Summit Organizing Committee, which begins in Hong Kong on Tuesday. "We do not know what will be said" when He speaks during a session on the processing of human embryo & # 39; s.
Organizing committee member Dr. George Daley, Dean of Harvard Medical School, said he was invited to speak at the top because of a 2017 lecture he gave at Cold Spring Harbor Laboratory about editing taken in embryos from humans, ape and mouse. During that session he described the changing of target DNA in human embryos made by in-vitro fertilization, resulting in a few unintended operations ("off-target effects"). The main problem was that only a few cells of the embryo were successfully processed, resulting in so-called mosaicism.
But he then said that he was able to increase the proportion of processed cells by injecting the very early embryos twice with CRISPR-Cas9: once when they consisted of only a single cell, and again when they were out of two. cells existed.
In his lecture in 2017 he had not said that he intended to use the processed IVF embryos to start a pregnancy. He finished his presentation stating the case of Jesse Gelsinger, whose death in 1999 in a gene therapy study, the much less precise precursor of genomics, has restored that field by more than a decade. He urged scientists who proceed to edit embryos to proceed slowly and "cautiously," since "a single instance of failure will kill the entire field."
His claim, first reported by the Associated Press, is not supported by a scientific article, leaving scientists in limbo about how well the genome is working. He used CRISPR-Cas9 to disable a gene called CCR5 that produces a receptor that allows HIV, which causes AIDS, to enter cells. People who do not have functional CCR5 genes are therefore immune to HIV infection.
A report from the National Academies 2017 on genomic editing identified CCR5 as a potential target for embryo processing by CRISPR-Cas9. "We discussed that, but it was not a focus of the report," said Bio-ethicist R. Alta Charo of the University of Wisconsin, who chaired the panel of academies that produced the report. Because editing an embryo changes its sperm or egg-producing cells or germ line, the changes would be passed on to future offspring.
Germline processing is considered to be more ethically fraught than using genomic editing to treat a child or adult, which would only change the blood-forming cells in a person with sickle cell disease and not hereditary DNA. Germline editing should therefore remove a higher ethical bar, Charo said on the eve of the genome editing summit: the risks and potential benefits for the child who would develop from a processed embryo should be carefully evaluated, said they.
In the case of the twins, all benefits are not clear. Their father is HIV positive and sperm can carry HIV, Daley said. But there are other ways to prevent a father from passing on HIV to his children, such as washing the sperm.
And HIV can be both prevented and treated, said biologist Richard Hynes of MIT, who attends the Hong Kong meeting and presided over the national academy panel: "We have set strict criteria that should be met" to justify embryo processing, he said . "It should only be for serious unmet medical needs, and informed consent should be present," all of these things must be looked at "to see if the Hot experiment meets the criteria. For example, on consent forms, parents were asked to sign. He called his work "development of AIDS vaccines", reported the AP, so it is not clear if the parents of the girls understood what he intended to do.
The risks of genomic editing in general include altering DNA other than the targeted genes, which could have unintended health consequences, and without a detailed scientific article, no one knows if CRISPR is the DNA of the girls everywhere has changed except in their CCR5 gene. The specific risks of having a disabled CCR5 gene include a higher risk of infection with the West Nile virus and the death of flu. He did not say whether he had clearly communicated those risks to the parents.
His work would be illegal in the United States, which prohibits processing of embryos, and in many other countries.
Watchdog groups quickly denounced His work. "If this is true, it comes down to unethical and reckless experimenting with people, and a serious abuse of human rights," said Marcy Darnovsky, executive director of the Center for Genetics and Society, in a statement. "We wish the best for the health of these babies, but strongly condemn the stunt that threatens their safety and endangers the rest of us." Opening the door to a society of genetic haves and have-nots undermines our opportunities for a fair and just future. "
Concerns about & # 39; haves and heave-nots & # 39; refers to the fear that the processing of embryos for desired characteristics will one day be available for parents who can afford it, which aggravates social inequality.
"It is possible that in the circumstances [the experiment] was considered justified, "Robin Lovell-Badge of the London-based Francis Crick Institute told journalists on Monday before the genomic editing summit." But we just do not know that. We have to wait to hear from him, "he said, referring to the upcoming top presentation of He.